The mechanism of action of quinidine on the sinus node studied by direct perfusion through its artery

Abstract

Studied by direct perfusion of the sinus node through its artery, quinidine has three actions: direct, anticholinergic, and antiadrenergic. The direct action of quinidine is insignificant at concentrations below 10.0 μg per milliliter, but causes suppression of sinus activity at 100 μg per milliliter. The anticholinergic and antiadrenergic actions occur concurrently and are unrelated to the direct action: both of these effects increase in direct relation to the concentration of quinidine. Since the autonomic blocking effect includes both nerve stimulation and the administration of local neurohormones, this action of quinidine occurs at the receptor site and is not due to inhibition of local release of effector substance.